This is known as the criticality condition. Here's why:
* Chain Reaction: Fission reactions release neutrons, which can then cause other atoms to fission, creating a chain reaction.
* Self-Sustaining: To be sustainable, the chain reaction needs to continue indefinitely. If each fission produces fewer than one new fission, the reaction will die out. If it produces more than one, the reaction will become uncontrolled and potentially dangerous.
* Criticality: The point where each fission produces exactly one new fission is called criticality. This is the point where the reaction is self-sustaining without increasing or decreasing in intensity.
Important Note: The actual number of neutrons released per fission varies depending on the specific isotopes involved. However, on average, a sustainable chain reaction requires the production of one additional fission per original fission.
